CAREER: Investigating Strong Electron-Phonon Interactions in Semiconducting Crystals Using Reciprocal-Space Quantum-Classical Modeling

在化学系化学理论、模型和计算方法（CTMC）项目的支持下，西北大学的Roel Tempelaar将研究用于光电器件和信息技术的半导体材料中电子和核振动（声子）之间的强相互作用。各种变革性材料的电子-声子耦合强度超过了常用半导体，实现了全新的功能，但也促使人们需要新的预测理论方法，将准确性与可扩展性结合起来。Tempelaar和他的团队旨在通过发展量子力学描述电子而经典描述原子核的方法来解决这一需求。通过采用所涉及的坐标的动量表示，可以模拟超大尺寸的材料。这为定量理解和控制材料行为开辟了道路，对太阳能的有效收集和量子态在节能和安全信息技术中的使用具有重要意义。这项研究与解决经济上处于不利地位的附近高中生的代码文盲的教育组成部分相结合。该组件旨在通过构建基于丰富的智能手机技术的编码练习序列，促进课堂环境之外的编码暴露。在各种新兴的晶体半导体中，包括金属卤化物钙钛矿和过渡金属二硫族化合物，电子-声子耦合比通常在无机材料中发现的更强。虽然这种耦合强度产生了独特的光物理性质，但它们提出了非微扰建模的需要，以揭示其机制原理。Tempelaar和他的团队试图通过根据通常用于描述晶体激发的布洛赫态重新制定量子经典动力学方法来解决这一需求。在Bloch表示中，可以执行基截断，这将大大降低模拟的成本。这将使团队能够解决光激发的演变，手性声子模式产生的光物理学，以及现实条件下六边形晶格中耦合自旋动量态的动力学。通过这个研究项目，Tempelaar团队的研究生和博士后研究人员将接触到理论化学、物理和材料科学的结合技术，培养他们成为跨学科的科学家。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

With support from the Chemical Theory, Models and Computational Methods (CTMC) program in the Division of Chemistry, Roel Tempelaar of Northwestern University will study strong interactions between electrons and nuclear vibrations (phonons) in semiconducting materials for use in optoelectronic devices and information technologies. Various transformative materials feature electron-phonon coupling strengths exceeding those seen for commonly-used semiconductors, enabling radically new functionalities, but also prompting the need for new predictive theoretical methodologies that combine accuracy with scalability. Tempelaar and his team aim to address this need by developing methods where electrons are described quantum-mechanically while nuclei are described classically. By adopting a momentum representation of the involved coordinates, materials of exceedingly large sizes can be simulated. This opens ways to quantitatively understand and control material behaviors, with implications for the efficient harvesting of solar energy and the use of quantum states for energy-efficient and secure information technologies. This research is integrated with an educational component addressing code illiteracy among economically-disadvantaged nearby highschoolers. This component aims to foster coding exposure beyond a classroom environment by constructing an engaging sequence of coding exercises based on abundant smartphone technology.In various emerging classes of crystalline semiconductors, including metal-halide perovskites and transition-metal dichalcogenides, electron-phonon couplings are stronger than typically found for inorganic materials. While such couplings strengths give rise to unique photophysical properties, they pose the need for non-perturbative modeling in order to unravel their mechanistic principles. Tempelaar and his team seek to address this need by reformulating quantum-classical dynamical methods in terms of Bloch states commonly used to describe crystal excitations. Within the Bloch representation, basis truncations can be performed that will significantly reduce the cost of simulations. This should enable the team to address the evolution of photo-excitations, the photophysics emerging from chiral phonon modes, and the dynamics of coupled spin-momentum states in hexagonal lattices under realistic conditions. Through this research program, graduate students and postdoctoral researchers in the Tempelaar team will be exposed to a combination of techniques from theoretical chemistry, physics, and materials science, fostering their development as cross-disciplinary scientists.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.